I. Field of the Invention
The present invention relates generally to impact absorbing, load decelerating devices. More specifically, the invention relates to a load decelerating or impact damping or absorbing device that is primarily oriented horizontally for absorbing impact forces at the rear of a truck trailer.
II. Description of the Prior Art
Shock absorber or impact dissipating devices are used to dissipate the considerable forces engendered by colliding masses. If the shock absorber is too small or large, a potentially damaging impact spike can occur. On the other hand, on some high efficiency designs, if the speed is too high, (or too low) deceleration efficiency is lost and safety must be sacrificed, subjecting the protected vehicle/craft to greater risks from undesirable breakage, collapse, stress and the like.
As will be recognized by those skilled in the art, shock absorbers and other load decelerating devices decelerate masses and reduce kinetic energy through displacement. Low velocity air drop means were originally developed by the military to quickly transport important materials in combat situations. They continue to be used extensively by several segments of the military for these job duties.
Typical low velocity air drop devices carry their loads on cables or "slings" extending between the load and the free-fall arresting means. An obvious and significant advantage of parachutes over other conventional delivery means is their mobility and reduced speed at impact. For example, when troops touch ground they intentionally fall in a way so as to dissipate the force of the impact over time and distance. Likewise, equipment/cargo is sometimes placed on a collapsible pallet to do the same thing. Devices and methods that dissipate impact energy in "vertical" applications such as air drops also have relevance in "horizontal" applications, such as crash protection and the like.
For example, force impact resistant systems are in widespread use with automobiles. A problem associated with energy absorbing bumpers involves movement during impact. The effectiveness of known cost-effective impact dissipation systems is reduced non linearly in response to vehicle speed. Many impact resistant bumpers are of little benefit at speeds over five miles an hour. At highway speeds known impact dissipating systems fail to prevent catastrophic collapse and resultant personal injury. Such collapse may result in load jettisoning or the total loss of vehicle structural integrity. Obviously occupant safety is sacrificed as well.
A wide variety of crash attenuators have been used to decelerate an impacting vehicle which has left the highway, including attenuators based on dispersible inertial materials such as sand, valved fluids such as water, disintegrating materials such as vermiculite, and buckling columns. These previous embodiments of impact attenuating devices adapted to be mounted on a vehicle have generally been of the type comprising an energy absorbing element and a mounting arrangement coupled to the energy absorbing element and configured to mount the energy element on the vehicle. These devices are often referred to in the industry as a truck mounted attenuator or TMA and are typically mounted on the rear of the vehicle. These prior art TMAs are generally large box like structures containing the energy absorbing material and extend out from the rear of the mounting vehicle. These prior TMAs are large and unsuitable for general use on a vehicle operating at normal highway speeds.
Due to new safety requirements imposed on the commercial tractor trailer manufacturers, there are recognized opportunities to make improvements to the rear bumpers of large over the road trailers to provide protection to the occupants vehicles involved in rear end collisions with these trailers. In looking at these opportunities we recognize some basic requirements for the acceptance of new and innovative approaches. These include: Cost comparable to savings or benefit; Reduction in predictable injuries, (both from under ride prevention and from impact forces transposed to the vehicle occupants); and Acceptance by the Regulators and Documentation of Benefit.
U.S. Pat. No. 5,106,137 deals with a gas in response to vehicle impact. U.S. Pat. No. 4,085,832 deals with a plurality of axially aligned chambers. Whereas mine would have different stress density stages, but would also have an anti-rebound means for use with elastic absorbers. U.S. Pat. No. 4,079,926 shows a composite coil providing a means of preloading the coil. U.S. Pat. No. 4,022,451 deals with an impact damping system with a progressively tighter fit as it telescopes. U.S. Pat. No. 4,441,751 deals with a device that substantially protrudes from a vehicle to provide a cushion against the shock of impact. U.S. Pat. No. 4,929,008 shows staged impact absorbing means of friction against slotted bolted surfaces and an inflatable block. U.S. Pat. No. 4,514, 002 shows a two position bumper, whereas my present invention shows a substantially fixed position bumper with a designated path to retract with impact and remain captured, following severe impact until gradually released by personnel following a procedure.
Using the three plane motion in my helicopter device as a contemplated means to allow impact strikes in a slightly offset direction would be applicable in more sophisticated applications (such as air drop to irregular terrain).
The known prior art does not adequately address the need for an efficient, quick operating, shock absorbing suspension stabilizer for this range of speed. While the prior art includes systems for decelerating a mass, known systems do not intentionally shift the mechanical advantage of the shock absorbing apparatus. Prior art devices do not resist the impact while progressively retracting due to impact to absorb the energy of high speed collisions while limiting the travel distance to that beyond which passenger compartment intrusion injuries could occur.